Drill bit construction

ABSTRACT

A drill bit construction, particularly adapted to rotary drill bits employing diamonds or like cutting elements includes a secondary cutting means disposed within the bit body and independently rotatable with respect to the bit body. The cutting face of the secondary cutting means is exposed to and overlies that portion of the borehole below the axis of rotation of the bit, and will efficiently drill that portion of the formation beneath the axis of rotation of the bit, which in conventional bit construction would be exposed to cutting elements having a velocity approaching zero.

Lehonrg [54] lDRlllLlL BET (IUNSTRIUQTKQN [72] Inventor:

Plaza, Suite 428, Houston, Tex. 77027 [22] Filed: .11une4, 19711) [21] Appl. No.: 43,503

[52] US. Cl 175/404, 175/330 [51] llnLCl ..lE21h9/116,E21c 13/02 [58] Field oiSenrch ..l75/65,67,329,330,333, 175/404 (56] References Cited UN lTED STATES PATENTS 2,619,325 11/1952 Arutunoff... ..175/330 X 2,877,988 3/1959 Cameron et a1 ..175/329 X 2,911,196 11/1959 Cameron et a]. ..175/329X 3,077,936 2/1963 Arutunoff 175/404 X 2,587,429 2/1952 Arutunofi 1 ..l75/333 2,667,334 1/1954 Ortloff ..175/333 X Maurice 11 Lehonrg, 3700 Greenway Koch ..175/330 3,084,752 4/1963 Tiraspolsky 1 75/404 3,424,258 1/1969 Nakayamn ..l75/333 Primary Examiner-David H. Brown A!t0mey- Arnold, White fit Durkee, Tom Arnold, hill Durkee. Jack C. Golcistein, John F. Lynch, Louis '11. Pirkey, Frank S. laden, 11! and Robert A. White 16 (Claims, 41 Elli-owing more;

hlhlllLlL nrr consrnncrion BACKGROUND AND PlRlOlR ART The instant invention relates to a novel construction for rotary drill bits. More particularly, the instant invention is directed to a rotary drill bit construction which is useful in bits using hard cutting elements such as diamonds or the like and in which bits it is customary to form a central core within the bit to centralize and stabilize the bit for the drilling operation.

Drill bits utilizing diamonds or similar hard cutting elements are commonly employed in drilling operations, particularly in hard subterranean formations such as chert or the like. The construction of such diamond drill bits usually includes a body portion having means for interconnection of the bit into a drill string, and a matrix portion for mounting the diamonds or other cutting elements. Drilling fluid is directed down to the bottom of the borehole through the drilling string which is in communication with a port generally disposed in the central portion of the bit. Fluid passageways or water courses across the drilling surfaces of the bit are also provided to transport the drilling fluid across the face of the bit to cool and lubricate the drilling surface and to facilitate the removal of drill cuttings from the drilling area.

it is also customary in diamond bit construction to provide a central passageway or concave section in the lower face of the bit which results in a formation of a generally conically shaped rock core beneath the bit which assists in centering the bit and provides additional projected area for placement of diamonds near the center of the bit. Since as the axis of rotation of a diamond bit is approached, the velocity of the diamonds with respect to the formation decreases to virtually zero, the very central portion of the formation beneath the axis of rotation of the bit presents a problem. in the area of the formation immediately below the axis of rotation of the bit, the drill bit is effectively placing a columnar load upon the formation and progress is made primarily by crushing the formation beneath this columnar load. Since diamond bits and bits of this type are customarily used in hard formations, disposing of this central portion of the formation by crushing is quite ineffective.

Accordingly, as mentioned above, concave sections are often provided in the central portion of the lower face of the bit to enable concentration of additional diamonds or other hard cutting elements in that area to assist in crushing the formation. Customarily, the largest'diamonds in a diamond drill bit are located in this central area.

Alternatively, a central passageway may be provided in the bit permitting the formation of a generally conically shaped core which is primarily abraded from the side by the interior drilling surfaces of the bit. Other bit constructions tend to encourage the formation of a fairly long rock core which is progressively thinner as it progresses up the center of the bit in hopes that the rock core will be fractured along its length and disposed of. in these latter instances, it is necessary to provide sufficiently large openings in the upper portion of the bit to enable the drilling fluid to carry away any large pieces of the central core which might break off.

A solution along these latter lines is offered in US. Pat. No. 2,931,630 which provides a drill bit which encourages the formation of a central core and provides for a core passageway extending from the recess which receives the core to the exterior of the bit.

In such construction, it is clearly possible that a large piece of core could jam in the bit and thereby decrease drilling efficiency.

SUMMARY OF THE lNVlENTlQN There is accordingly provided by this invention a novel rotary drill bit which includes means to effectively drill the central portion of the formation underlying the axis of rotation of the bit.

There is further provided by the instant novel drill bit, a construction wherein a cutting surface is provided over that portion of the formation beneath the axis of rotation of the drill bit, which cutting surface has cutting elements which have a velocity with respect to the formation.

There is also provided in accordance with this invention a novel rotary drill bit having a second cutting face overlying the formation beneath the axis of rotation of the bit, which cutting face is caused to move across the formation in a direction opposite to the direction of rotation of the bit by virtue of frictional forces imposed upon this cutting face by the formation.

The novel rotary drill bit in accordance with this invention comprises a drill body having cutting elements embedded therein to provide a drilling surface; and a second cutting means, in addition to the drill face of the bit, mounted within the drill body and rotatable with respect to the drill body, the second cutting means having an axis of rotation eccentric to the axis of rotation of the drill bit and having a cutting surface which is open to and overlying that portion of the formation beneath the axis of rotation of the drill bit.

This secondary cutting face, by virtue of its disposition eccentric to the drill bit is propelled in a direction opposite to the direction of rotation of the drill bit when it is in contact with the formation. This independent rotation of the second cutting means propels its cutting elements across the surface of the formation at the very center of the drill bit and effectively drills this central part of the formation as opposed to crushing it.

lFluid passageways are provided adjacent this secondary cutting surface to remove cuttings from this region.

in accordance with the preferred embodiment of the invention, the secondary drilling face is disposed proximate the drilling face of the drill bit so that the secondary cutting surface drills that portion of the formation beneath the axis of rotation of the drill bit with the formation of a core of minimum size or, if desired, with formation of virtually no core at all.

BRIEF DESClRllTlON OF THE DRAWINGS The instant invention will be further described with specific reference to the embodiments of the instant invention specifically illustrated in the drawings.

FlG. l is a sectional view of a diamond drilling bit in accordance with the instant invention having a central channel for accepting a rather long core in the bit.

MG. 2 is a sectional view along line 2-2 of FIG. 1.

H6. 3 is a sectional view of a drill bit in accordance with the second embodiment of this invention wherein the size of the core is minimized.

FIG. 4 is a sectional view along line 4-4 of FIG. 3.

DESCRIIPTTON OF SPECEFIC AND PREFERRED EMBODlMENTS With reference to FIG. ll, there is illustrated a novel rotary drill bit in accordance with one specific embodiment of this in vention. Drill bit Ill is shown in place in a subterranean formation ill and includes an upper shank member 13 which is interiorly threaded for interconnection in drill string 12. Lower crown member of the bit has its lower portion faced with matrix 27 which is suitable for embedding cutting elements l9. These cutting elements, which may be diamonds, tungsten carbide particles or like metallic, intermetallic, or nonmetallic material, are possessed of sufficient hardness and abrade the formation. Such materials are well known in the art.

Matrix 27 is typically a hard abrasion and erosion resistant metal such as bronze, copper nickel alloy or the like, which can be cast upon crown member 15 to make a firm bond therewith. The lower portion of crown member 15 is provided with a central passageway, shown in FIG. 1 to be occupied by central core 2i produced as the bit drills the fomtation. Cutting elements R9 are embedded in the matrix by means known in the art defining a semitoroidal drilling surface for the bit which includes a reaming or gage face 22, a downward drilling face 2d, and a generally frustoconical inner coring face 118.

During use, drilling fluid is directed to the bit through the interior to of drill string i2 and thence to the bit through a series of passages 17 in shank member 13 and ultimately across the face of the bit in fluid passageways or water courses 233. These fluid passageways 23 take the form of grooves or channels in the matrix 2'7 which traverse the drilling face of the bit and extend from interior surface 18 across drilling face 2d and up reaming face 22 of the bit, emptying into volume 25 above shoulder 24. These passageways serve to supply drilling fluid to the drilling surfaces of the bit to lubricate, cool and remove cuttings from the region of the cutting elements.

Shank member 13 is firmly but preferably removably secured to crown member 15, for example by suitable threads shown at 30. Disengagement of the crown member from the shank member is desirable in the bit construction shown in FIG. 1 in order to accomplish replacement or repair of the cutting wheel as will be appreciated hereinbelow. This uncoupling ability in the bitshown in lFlG. B provides a bit in which the shank portion can be adapted to fit a number of crown members having somewhat varying placement arrangements of cutting elements. Varied designs of drilling bits, particularly diamond drilling bits, to meet specific downhole conditions are known in the art, and any such design which leaves the cutting wheel exposed to the formation in order to drill central core 21l could be used.

Between shank member i3 and crown member 115, there is provided volume 29 through which drilling fluid passes on its route down to the drilling surfaces of the bit. Rotatably mounted in shank member 113, and extending into volume 29, is cutting wheel 31 which has a flat cutting face 33 in which are also embedded cutting elemenu 35 which may also be diamonds or similar hard cutnng elements. The cutting wheel is mounted with a thick bearing portion 32 being received into shank member 13 for strength. Cutting wheel 31 is adapted to be freely rotatable about an axis M-M, which axis is eccentric of the axis of rotation L-L of the bit itself, and is provided with thrust bearing 39 and O-ring seal 37 to preclude intrusion of fluid or drilling debris to the bearing surfaces of the cutting wheel. When not bearing against the core, cutting wheel 31 will fall slightly and rest against the upper surface of crown member l5. if desired, a detent means may be used to retain it in its illustrated position. Of course, any other suitable mounting method for cutting wheel 311 permitting the free rotation around an axis eccentric to the axis of the drill bit might be used.

Volume 29 is designed to be somewhat larger than would be necessary merely to accommodate cutting wheel 31. Cuttings from cutting wheel $1 must be readily accommodated within volume 29 without sticking until such cuttings can be removed through water courses 23. Note that at least one fluid passage 36 similar to passages l? is located to the right-hand side of cutting wheel 31 to prevent accumulation of cuttings in the right-hand portion of volume 2.9.

if desired, the surface of cutting face 353 of cutting wheel 31 can be provided with shallow ridges or recesses across the cutting face between the cutting elements to enable drilling fluid flow around the cutting elements to cool and lubricate them and to assist in carrying away cuttings from the cutting wheel. Such shallow grooves are illustrated at 34. These grooves or recesses are quite shadlow and are not expected to carry as much fluid as water courses 23 across the drilling face of the bit.

in operation, as the bit is rotated, drilling fluid is supplied through the drilling string 12 and fills volume 29 prior to escaping across the drilling surface of the bit through passageways 23. As drilling'proceeds, the interior faces lid of the bit cause the formation of a columnar core 2i which eventually extends upward beyond the cutting elements of interior face 18 and contacts the cutting face 33 of cutting wheel 311.

With reference now to MG. 2, arrow A indicates the normal direction of rotation of drill bit llll. Core 2i is shown contacting the surface of cutting wheel 3i with the entire area of such contact on one side of the center of rotation lb of cutting wheel M. As downward force is applied on drill bit llll the cutting face 335 of the cutting wheel frictionally engages the upper surface of core 23. As rotation of the bit is commenced, frictional forces perpendicular to the axis of cutting wheel 31 are exerted upon the cutting wheel by the core 2i. Assuming that the core is uniform in consistency, the amount of frictional force (or more smcifically the amount of frictional resistance to hit rotation) exerted by the core on face 33 will be uniform over the entire area in which the core contacts face 33. These relative forces exerted between core member 2! and cutting face M can, under these circumstances, be resolved as two vectors X and Y acting upon the cutting wheel 31 in the manner shown in H6. 5. Since vector X is somewhat larger than Y and is, by virtue of the eccentric axis of rotation of the cutting wheel, acting on a longer lever arm than vector Y, the cutting wheel 311 will be caused to rotate in the direction indicated by arrow B.

The face 35 of cutting wheel 33 will move across and traverse the top surface of core 21 and accordingly will slowly drill the top of the core. Thus it can be seen that even at the very center of rotation of the drill bit there is provided a cutting surface which does not have a zero velocity with respect to the core.

With reference now to FIG. 3, there is shown a drill bit in accordance with an alternate and preferred embodiment of the invention. Drill bit 511 is provided with means (not shown) for interconnection in a drill string. As in the previously discussed embodiment, bit 51 is provided with a body member 52 which is cast with a matrix 59 having cutting elements 58. The body member is also provided with fluid channels 55 which are in fluid communication with the supply of fluid in the drill string and which direct fluid into fluid passageways or water courses 57 across the face of the bit to empty above shoulder 59 and space oil. Cutting wheel 71, with a cutting face 73 embedded with cutting elements 75 as above, is mounted in member 72 bolted with bolts to body member 52 and adapted to rotate about axis 0-0 which is eccentric of the axis of rotation of the bit N-N. Cutting wheel 71 is mounted in the body with a thrust bearing 77 and an O-ring seal 79 together with pins 91 which pass through member 72 and lodge. in grooves 93 to retain the wheel in member 72.

The design of the embodiment of HO. 3 differs from the embodiment of HG. l in that cutting wheel 71 is mounted with its surface not far above the downward cutting face 60 thus affording for formation of a much shorter central cone 63 as the formation is drilled. An eccentric opening in the lower face of the bit exposes the entire cutting surface 73 of cutting wheel "ill to the formation. Since interior coring face 62 will form a conical core of the shape indicated at 63, however, the core will contact the face 73 of the cutting wheel only as indicated on the left-hand side of axis 0-0. The bit of FIG. 3 will otherwise operate similarlyto that described in FIG. 1. The elimination of the coring face in the right-hand portion of the bit as illustrated, however, leaves available volume 67 within opening (55 in which any large cuttings from the core can fall and thereby be emily removed from the cutting region without clogging the bit.

in the embodiment of lFlG. ll, it is possible that the columnar core might break off proximate the hole bottom and become wedged or stuck in the interior opening of the bit. it can be readily seen that if such were to occur, drilling efficiency would suffer. Accordingly, by placing cutting wheel 7i nearer the downward drilling face bill of the bit, the size of the col umnar core is minimized, and by exposing the entire face of the cutting wheel, a volume such as 67 is made available to accommodate cuttings from the cutting wheel with minimum risks of clogging the bit. The disposition of cutting wheel 71 with respect to the lower drilling face can be selected primarily in view of the size of the conical core desired to be produced for centering purposes. Of course, it is understood that the cutting face of cutting wheel 711 must be disposed somewhat above the drill face so since the cutting face will not function as intended if its entire surface is in contact with the formation.

The cutting wheels shown in the embodiment illustrated are shown as having substantially flat cutting surfaces, and such flat cutting surfaces are preferred. As pointed out above, it is desirable to provide shallow ridges traversing the cutting face of the cutting wheel in order to enable drilling fluid to flow around the cutting elements to cool and lubricate them and to assist in carrying away cuttings from the cutting wheel. However, it should be understood that other shapes for cutting wheels may be used and accordingly, wheels with concave or convex toroidal cutting surfaces or the like may be employed.

The cutting wheel may be disposed in any desired fashion with respect to the body of the bit so long as it is eccentrically disposed over the core formed by the interior faces of the bit. However, it is preferred that the entire core surface contact the cutting wheel substantially on one side of the axis of rotation of the cutting wheel, since such disposition is more conducive to independent cutting wheel rotation.

Other modifications in the design of bits in accordance with this invention may be made as will be appreciated by those skilled in the art. For example, it may be desirable to direct jets of fluid from passages such as passage 17 in the bit directly against the central portion of the core being drilled by the cutting wheel in order to assist in that operation. A similar modification of the embodiment shown in MG. 3 might also be accomplished to direct a jet stream of drilling fluid against the core to assist the drilling operation of the cutting wheel.

Other obvious design modifications may also be made utilizing the concept of this invention. This invention may be adapted to variety of diamond bits and other bits which have a design which promotes the formation of a central core beneath the axis of rotation of the bit and of course may be adapted to the various bit designs known in the art such as stepped face bits, eccentric bits or the like. Other modifications will also be suggested to those skilled in the art upon a reading of this disclosure.

I claim:

1. A rotary drill bit comprising:

a drill body having cutting elements to provide drilling surface and adapted to form a core; and

means mounted in said drill body and being freely rotatable with respect to said drill body;

said means being disposed entirely within the drilling circle defined by the outermost of said cutting elements and having an axis of rotation which is eccentric of and parallel to the axis of rotation of said drill bit, and

said means having a substantially flat cutting surface disposed above the lowermost drilling surface of said drill bit;

said cutting surface being open to and overlying the core formed beneath the axis of rotation of the bit.

2. The rotary drill bit of claim 1 including fluid pamageways in said drill body for providing fluid to the vicinity of the cutting surface of said means.

3. The rotary drill bit of claim ll including a plurality of cutting elemenm disposed upon the cutting surface of said means, and shallow ridges on the cutting surface of said means between said cutting elements to afford access of drilling fluid to said cutting elements during drilling.

4. The rotary drill bit of claim ll wherein the cutting elements on said drill bit are diamond cutting elements.

5. The rotary drill bit of claim ll including:

means in said drill body defining a central opening in the bottom of the drill body, said opening having an axis eccentric to the axis of rotation of the bit; and

interiorly facing cutting elements disposed on the lateral surface of said opening to produce a central upstanding formation core below the axis of rotation of the bit; wherein said means rotatable with respect to the drill body is disposed in said opening with its cutting above the lowermost cutting surface of said drilling surface of the bit. 6. The rotary drill bit of claim 5 wherein said means rotatable with respect to the drill body is disposed with its axis sufficiently eccentric of the axis of rotation of the bit that said central upstanding core contacts the cutting surface of said means on one side of the axis of rotation of said means.

7. The rotary drill bit of claim ll wherein said drill body comprises a shank member and a crown member having a central opening therein and removably attached to said shank member and including:

means defining a volume between said shank member and said crown member; and

means mounting said means rotatable with respect to the drill body in said shank member with the cutting surface of said means disposed in said volume above said central opening.

8. The rotary drill bit of claim 7 including means for providing a flow of drilling fluid to said volume.

9. The rotary drill bit of claim 1 wherein there is an opening in the central lower portion of said drill surfaces to form and receive a centering core as the said bit drills a formation.

MD. The rotary drill bit of claim 9 wherein the cutting surface of said means is disposed in said central opening overlying the portion of the formation beneath the axis of rotation of the bit.

M. The rotary drill bit of claim lltl wherein said means is disposed sufficiently eccentric of the axis of rotation of said bit that the upper surface of said centering core, contacts the cutting surface of said means on one side of the axis of rotation of said means.

l2. A rotary drill bit comprising:

a drill body having cutting elements and having an opening in the lower portion thereof for receiving an upstanding core at me center of the hole being drilled;

cutting elements disposed on said drilling body to describe a drilling surface having an outward reaming face, a downward drilling face, and an inner coring face within said opening; and,

secondary cutting means mounted in said drill body entirely within the drilling circle defined by said reaming face to be freely rotatable with respect to said drill body about an axis eccentric of and parallel to the axis of rotation of said bit, said cutting means having a substantially flat cutting surface disposed above the lowermost drilling face of said drill body and overlying said upstanding core.

13. The rotary drill bit of claim 12 including a plurality of cutting elements disposed upon the cutting surface of said secondary cutting means and shallow ridges on the cutting surface of said secondary cutting means between said cutting elements to afford access of drilling fluid to said cutting elements during drilling.

M. The rotary drill bit of claim 12 wherein the cutting ele ments disposed on said drill body are diamond cutting elements.

lid. The rotary drill bit of claim 12 wherein said opening in the lower portion of said drill body is eccentric of the axis of rotation of said bit and exposes the entire cutting surface of said secondary cutting means.

36. The rotary drill bit of claim l5 including:

means for interconnection of said drill body with a drilling string;

first fluid passageways in said drill body between said drilling string and said opening in the lower portion of said drill body to permit flow of drilling fluid from said drill string to said opening; and

second fluid passageways across the face of said bit from said opening to a region removed from the drilling area of the bit.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated January 18, 1972 Patent No.

Inventor(s) Maurice our'g It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Fin. 1 of the drawings, the designation "25" should be reflected as follows Signed and sealed this 26th day of September 1972.

(SEAL) Attest:

Commissioner of Patents USCOMM-DC 6O375-P69 U.S. GOVERNMENT PRINTING OFFICE I969 0-366-334 FORM PO-I 050 (10-69) 

1. A rotary drill bit comprising: a drill body having cutting elements to provide drilling surface and adapted to form a core; and means mounted in said drill body and being freely rotatable with respect to said drill body; said means being disposed entirely within the drilling circle defined by the outermost of said cutting elements and having an axis of rotation which is eccentric of and parallel to the axis of rotation of said drill bit, and said means having a substantially flat cutting surface disposed above the lowermost drilling surface of said drill bit; said cutting surface being open to and overlying the core formed beneath the axis of rotation of the bit.
 2. The rotary drill bit of claim 1 including fluid passageways in said drill body for providing fluid to the vicinity of the cutting surface of said means.
 3. The rotary drill bit of claim 1 including a plurality of cutting elements disposed upon the cutting surface of said means, and shallow ridges on the cutting surface of said means between said cutting elements to afford access of drilling fluid to said cutting elements during drilling.
 4. The rotary drill bit of claim 1 wherein the cutting elements on said drill bit are diamond cutting elements.
 5. The rotary drill bit of claim 1 including: means in said drill body defining a central opening in the bottom of the drill body, said opening having an axis eccentric to the axis of rotation of the bit; and interiorly facing cutting elements disposed on the lateral surface of said opening to produce a central upstanding formation core below the axis of rotation of the bit; wherein said means rotatable with respect to the drill body is disposed in said opening with its cutting above the lowermost cutting surface of said drilling surface of the bit.
 6. The rotary drill bit of claim 5 wherein said means rotatable with respect to the drill body is disposed with its axis sufficiently eccentric of the axis of rotation of the bit that said central upstanding core contacts the cutting surface of said means on one side of the axis of rotation of said means.
 7. The rotary drill bit of claim 1 wherein said drill body comprises a shank member and a crown member having a central opening therein and removably attached to said shank member and including: means defining a volume between said shank member and said crown member; and means mounting said means rotatable with respect to the drill body in said shank member with the cutting surface of said means disposed in said volume above said central opening.
 8. The rotary drill bit of claim 7 including means for providing a flow of drilling fluid to said volume.
 9. The rotary drill bit of claim 1 wherein there is an opening in the central lower portion of said drill surfaces to form and receive a centering core as the said bit drills a formation.
 10. The rotary drill bit of claim 9 wherein the cutting surface of said means is disposed in said central opening overlying the portion of the formation beneath the axis of rotation of the bit.
 11. The rotary drill bit of claim 10 wherein said means is disposed sufficiently eccentric of the axis of rotation of said bit that the upper surface of said centering core contacts the cutting surface of said means on one side of the axis of rotation of said means.
 12. A rotary drill bit comprising: a drill body having cutting elements and having an opening in the lower portion thereof for receiving an upstanding core at the center of the hole being drilled; cutting elements disposed on said drilling body to describe a drilling surface having an outward reaming face, a downward drilling faCe, and an inner coring face within said opening; and, secondary cutting means mounted in said drill body entirely within the drilling circle defined by said reaming face to be freely rotatable with respect to said drill body about an axis eccentric of and parallel to the axis of rotation of said bit, said cutting means having a substantially flat cutting surface disposed above the lowermost drilling face of said drill body and overlying said upstanding core.
 13. The rotary drill bit of claim 12 including a plurality of cutting elements disposed upon the cutting surface of said secondary cutting means and shallow ridges on the cutting surface of said secondary cutting means between said cutting elements to afford access of drilling fluid to said cutting elements during drilling.
 14. The rotary drill bit of claim 12 wherein the cutting elements disposed on said drill body are diamond cutting elements.
 15. The rotary drill bit of claim 12 wherein said opening in the lower portion of said drill body is eccentric of the axis of rotation of said bit and exposes the entire cutting surface of said secondary cutting means.
 16. The rotary drill bit of claim 15 including: means for interconnection of said drill body with a drilling string; first fluid passageways in said drill body between said drilling string and said opening in the lower portion of said drill body to permit flow of drilling fluid from said drill string to said opening; and second fluid passageways across the face of said bit from said opening to a region removed from the drilling area of the bit. 